Gasoline fuel compositions



GASOLINE FUEL COMPOSITIONS Samuel M. Darling, Lyndhurst, Ohio, assignor to The sagtlllill'd Oil Company, Cleveland, Ohio, a corporation o No Drawing. Application December 29, 1953 Serial No. 401,038

4 Claims. (Cl. 44-69) The present invention relates to a gasoline motor fuel containing tetraethyl lead and an alkyl sulfite and to the use, in operating an internal combustion engine, of a dialkyl sulfite as an agent for suppressing an increase in the octane requirement of an engine.

' It is well known that the operation of an internal combustion engine, initially clean, results in a formation of progressively greater amounts of deposits on the surfaces of the combustion zone, i. e., on the cylinder head, piston top and the intake and exhaust valves, until the amount ofdeposits reaches a level beyond which no appreciable further increase in amount of deposits is apparent upon continued operation. This increase in deposits is manifested most clearly to the operator of the engine, particularly an automobile engine, by the fact that the presence of the deposits in the engine requires a fuel having a higher octane rating in order not to knock than is required by a new or clean engine. This means, in other words, that the octane value of a fuel required by an engine containing deposits in the combustion zone in order not to knock (referred to hereinafter as octane requirement) is higher than the octane requirement of a clean engine. For example, a clean engine which requires a gasoline having an octane rating of 60 in order not to knock is said to have an octane requirement of 60. If the same engine, when dirty, i. e., with deposits in the combustion chamber, requires a gasoline having an octane rating of 75 in order not to knock, such an engine is said to have an octane requirement of 75 or an octane requirement increase of 15. When upon continued use the octane requirement of the engine increases no further, it is believedthat the engine has then reached deposit equilibrium. This is believed to be due to the fact that after acertain amount of deposits has been formed in the combustion zone, additional amounts of deposits either fail to adhere to the deposits already formed or the rate of formation of additional deposits becomes about equal to the rate at which the deposits flake ofi and are removed through the exhaust of the engine.

The undesirable elfects of the deposits in the combustion zone are-further aggravated when tetraethyl lead is contained in the fuel in knock-suppressing amounts varying between about 0.5 and 6 cc./gal., e. g., about 3 cc./ga1., because these deposits are then no longer primarily carbonaceous but contain appreciable quantities of lead or lead compounds. It has been sought to overcome this additional disadvantage due to the use of tetraethyl lead by adding one or more organic halides to the fuel so that, during the combustion, the lead from the tetraethyl lead will combine with the halogen from the organic halide to form a lead halide that will pass out of the engine through the exhaust manifold. While the addition of organic halide has helped, particularly in aviation engines which operate at higher temperatures than automotive engines, it has not been as successful as expected in the latter. This is apparently due to the relatively low volatility of lead halide at the temperatures maintained by automotive tes Patent cooling systems at the surfaces enclosing the combustion zone.

It has been found that the total weight of deposits formed in the combustion zone is appreciably greater when using a leaded fuel than when using a non-leaded fuel. The octane requirement increase of an engine operating on leaded fuel, however, is not in proportion to the difference in deposit weights. From this it is concluded that the octane requirement increase of an engine is not determined so much by the quantity of material deposited as by its presence and character.

Since it has been found that the octane requirement increase of an engine is not determined solely by the quantity of material deposited in the combustion zone, it is believed that it is due to a catalytic action wherein the deposits in the combustion zone act as catalysts to accelerate the oxidation of petroleum hydrocarbons. The fact that lead compounds have greater catalytic activity than carbon in accelerating the oxidation of petroleum hydrocarbons is believed to account for the greater increase in the octane requirement of an engine operated on leaded fuel as compared with that of an engine operated on non-leaded fuel. It was, therefore, believed that the proper approach to the problem of reducing the octane requirement increase of an engine was that of adding to the fuel a substance having an anti-catalytic effect or, in other words, the effect of suppressing or inhibiting the catalytic properties of the deposits formed, especially the troublesome lead-containing deposits.

It is generally known that organic sulfur compounds, such as alkyl sulfates, have been added to gasoline motor fuels containing tetraethyl lead with a view to stabilizing the tetraethyl lead and thereby preventing or minimizing cloud formation and deposition of deteriorated or partially decomposed tetraethyl lead in storage. Such sulfur compounds, however, generally have the undesirable property of reducing the lead response of the fuel. Some sulfur compounds, such as mercaptans and disulfides, are particularly detrimental in this respect in that they partially or completely inhibit the knock-reducing activity of the lead or preferentially react with the tetraethyl lead so that the lead added is not available to improve the octane rating of the fuel.

It has now been found, surprisingly, that even extremely small amounts of a dialkyl sulfite, or mixtures of dialkyl sulfites, in a gasoline motor fuel containing tetraethyl lead in a knock-suppressing amount are remarkably effective in suppressing the octane requirement increase in internal combustion engines run on gasoline motor fuel containing tetraethyl lead and that such addition of dialkyl sulfite, unlike addition of other organic sulfur compounds, does not reduce the lead response significantly. The presence in the fuel of one or more organic halides, as scavenger for the lead, does not interfere with the eifectiveness of the dialkyl sulfite.

The amount of dialkyl sulfite in the gasoline motor fuel is not particularly critical. However, it has been found that no appreciably better results are obtainable by increasing beyond 1:1 the molecular ratio of dialkyl sulfite to tetraethyl lead. On the other hand, significant effects are obtainable even when this ratio is as low as 1:100. It is preferable, therefore, in accordance with this invention, to have the molecular ratio of dialkyl sulfite to tetraethyl lead in the gasoline motor fuel range from about 1:100 to about 1:1, the optimum molecular ratio being between about 1:10 and 1:1.

The dialkyl sulfites suitable for use in accordance with the present invention are sulfites of the general formula R wherein R is a lower alkyl radical preferably containing from 1 to about 4 carbon atoms. Diethyl sulfite has been found to be particularly useful for the purposes of the invention.

One of the primary advantages of the gasoline motor fuel of the present invention is that so long as an internal combustion engine is operated with such fuel, there will be no perceptible increase in its octane requirement and hence no necessity for going through the expensive and time-consuming procedure of dismantling the engine periodically to scrape off the combustion chamber deposits and thereby restore the initial octane requirement of the engine.

This and other advantages, as well as the utility of the invention will become further apparent from the following examples, it being understood, however, that the examples are to be considered merely as illustrative and informative, and not limitative in scope.

EXAMPLE I Comparative test runs were conducted with a standard Chevrolet passenger car engine made initially clean after each run by dismantling, removing the combustion chamber deposits and reassembling. In each run the engine was operated on a standard cycle procedure to simulate city driving conditions. Each cycle included one minute at 500 R. P. M. with no load (idling conditions) and 5 minutes at 2000 R. P. M., equivalent to 40 M. P. H., with 11.2 lbs. brake horsepower load, an air fuel ratio of between 13.5 and 14.5, water outlet temperature of 165 F. and oil sump temperature of 195 F. In each run this 6 minute cycle was repeated for 72 hours, the equivalent to approximately 2900 miles of city driving. Octane requirement measurements were made under the following conditions:

Speed, R. P. M 1000.

Load throttle Full.

Jacket temperature 160 F. Spark advance 11 B. T. C.

In one of the 72 hour runs, conducted with gasoline containing 3 cc./gal. tetraethyl lead (0.015 mol/gal.), the octane demand increased by eight numbers. In another run conducted with the same motor gasoline containing the same amount of tetraethyl lead and in addition 2.0 -cc./gal. diethyl sulfite (0.015 mol/gal.), there was no'measurable increase in octane requirement.

This shows that dialkyl sulfites, which by themselves have no anti-knock effect, are extremely effective in suppressing the increase in octane requirement that normally takes place during operation of an internal combustion engine, particularly when it is operated on a gasoline motor fuel containing a knock-suppressing amount of tetraethyl lead.

EXAMPLE II Diethyl sulfite and diethyl sulfate were tested for their 4 efiect on lead response by a standard procedure well known in the art. The results of these tests are tabulated immediately below:

Eflect of diethyl sulfite and sulfate on lead response Tetraethyl lead, CC./gt1l. Additive Additive, Octane cc./gal F-l 1. A composition of matter consisting essentially ofgasoline, a knock-suppressing amount of tetraethyl lead and dialkyl sulfite, represented by the formula R wherein R is a lower alkyl radical containing from 1 to 4 carbon atoms, the dialkyl sulfite and tetraethyl lead being;

present in a molecular ratio ranging from about 1:100 to about 1:1.

2. A composition of matter consisting essentially of gasoline, a knock-suppressing amount of tetraethyl lead and dialkyl sulfite, represented by the formula R 80 wherein R is a lower alkyl radical containing from 1 to 4 carbon atoms, the dialkyl sulfite and tetraethyl lead being present in a molecular ratio ranging between about 1:10 and 1:1.

3. A composition of matter consisting essentially of gasoline, about 3 cc./gal. tetraethyl lead and about 2 cc./ gal. dialkyl sulfite, represented by the formula R 80 wherein R is a lower alkyl radical containing from 1 to 4 carbon atoms.

4. A composition of matter consisting essentially of gasoline, about 3 cc./gal. tetraethyl lead and about 2 cc./ gal. diethyl sulfite.

References Cited in the file of this patent UNITED STATES PATENTS 2,557,019 Morris et al June 12, 1951 

1. A COMPOSITION OF MATTER CONSISTING ESSENTIALLY OF GASOLINE, A KNOCK-SUPPRESSING AMOUNT OF TETRAETHYL LEAD AND DIALKYL SULFITE, REPRESENTED BY THE FORMULA R2SO3, WHEREIN R IS A LOWER ALKYL RADICAL CONTAINING FROM 1 TO 4 CARBON ATOMS, THE DIALKYL SULFITE AND TETRAETHYL LEAD BEING PRESENT IN A MOLECULAR RATIO RANGING FROM ABOUT 1:100 TO ABOUT 1:1. 